Stepped frequency radar for landmine detection attached to ......GPR UWB antenna 12 / 23 •There...
Transcript of Stepped frequency radar for landmine detection attached to ......GPR UWB antenna 12 / 23 •There...
Stepped frequency radar for landmine detection attached to hexacopter
Danijel Šipoš, Dušan Gleich, Marko Malajner
Univers ity of Mar ibor, S lovenia
16th International Symposium MINE ACTION,Slano, Dubrovnik-Neretva County, 10th April 2019
Outline of presentation• Motivation
• SFCW GPR • Theory
• Design
• Experimental results
• Conclusion• Future work
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Motivation: Idea• Cooperation with Bosnia and Herzegovina (University of Tuzla) where landmines still represent a serious problem
• Why to use RADAR on the drone: • Through the years RF components became even
smaller and more powerful
• Great progress on drones in the last few years
• Use of drones became popular also for many other applications and not only photography
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Possible lift up to 6 kg and flight time up to 20 min
Landmines• Types of landmines• Anti-personnel landmines - CHALLENGE• Anti-tank landmines
• Possible location of landmine• Above ground surface• Below ground surface - CHALLENGE
• Material of landmines• Metal landmines• Plastic landmines – CHALLENGE
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Ground penetrating radar (GPR)• The technical design of ground penetrating radars can be classified into two groups.
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GPR
Time domain
Baseband pulse
Noise-modulated
Frequency domain
SFCW FMCW
Stepped frequency continuous wave (SFCW) GPR
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• Working principle
• SFCW design
• UWB Antenna
• Experimental results
• Problems
SFCW GPR
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• Transmitter output
• Maximal measuring distance
• Resolution
„Synthetic pulse“ of SFCW radar sensor
SFCW GPR: Structures
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• Homodyne SFCW RADAR structure• RF input signal is downconverted once
• Super-Heterodyne SFCW RADAR structure• RF input signal is downconverted twice
• Disadvantages:• IQ imbalance because of phase shifter -> IQ
errors
• Requires a wideband quadrature detector
• Transmiter harmonics can cause ghost effects
SFCW GPR: Design
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• Homodyne structure (SFCW RADAR V1)
• Disadvantages• Ghost effects
• Phase / magnitude noise
SFCW GPR: Design
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• Super-Heterodyne structure (SFCW RADAR V2)• Synthesizer, FPGA, ADC and LO1 use same CLK
fsyn= 700 MHz
fLO1= 702 MHz
fLO2= 2 MHz
fmix_out= 2 MHz
External part
SFCW GPR: Design
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• Hardware parts
• Power
• Processing
• Transmitter
• Receiver
• Specifications
• Power con.: 350 mA
• RF power out.: +2 dBm
• Size: 100x50mm
• fstart = 700 MHz
• BW = 2 GHz
• tstep= 1 - 2 ms
GPR UWB antenna
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• There are many know types of UWB antennas • Resistively loaded dipole antenna• Bow-tie antenna• Spiral antenna• Horn antenna• Log-periodic antenna
Design of GPR antenna
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• Design of combined Horn and Vivaldi antenna
• Design and simulation was carried in CST Microwave Student Edition
A. Ahmed, Y. Zhang, D. Burns, D. Huston, and T. Xia, “Design of uwb antenna for air-coupled impulse ground-penetrating radar,” IEEE Geoscience and Remote Sensing Letters, vol. 13, no. 1, pp. 92–96, Jan 2016.
Antenna 3D model
Design of GPR antenna
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Simulation result
VNA measurement result (700 MHz – 3.9 GHz)
Antenna gain at 2.7 GHz (Max. approximately 9.9 dBi)
SFCW GPR: Solved hardware problems
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• Phase jump after frequency changeSolution: Use of directional coupler and RF switch for measuring a reference signal
• Antenna signal disturbing the receiver part• Solution: Using metal shielding for the SFCW PCB board.
• Antenna coupling• Solution: Antenna shielding between RX and TX antenna
SFCW GPR: Experimental results
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• Test measurement of coaxial cable lenght • Test RADAR measurement of reflector in air
SFCW GPR: Experimental results
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• B-Scan of AT landmine above ground surface• Landmine perimeter: 27 cm
• Landmine height: 13 cm
• Antenna distance to ground surface: 75 cm
AT landmine above ground
Raw Sub. Backg. With Gain
SFCW GPR: Experimental results
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• B-Scan of metal AP landmine above ground surface• Landmine perimeter: 7 cm
• Landmine height: 17 cm
• Antenna distance to ground surface: 75 cm
SFCW GPR: Experimental results
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• B-scan of plastic AP landmine below ground surface• Landmine perimeter: 7 cm
• Landmine height: 5 cm
• Antenna distance to ground surface: 45 cm
AP landmine below ground
Raw Sub. Backg. With Gain
SFCW GPR: Scan problems
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• Antenna distance to ground surface: 75 cm
• B-Scan test of buried metal stick at different antenna height
• Antenna distance to ground surface: 45 cm
Conclusion• The Pulse based GPR as also SFCW based GPR have shown positive results to detect above ground landmines as also buried landmines.
• The goal to develop a small sized GPR with standard IC components (low price) was achieved.
• Challenges• Landmine location
• Antenna to ground distance (Measure at greater distances from the ground surface)
• Future work on hardware improvement as also software improvement
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Conclusion: Future work• Hardware improvements • Metal shielding of whole RADAR system
• Separate shielding of Transmiter, receiver and RF switch
• Software improvements• On board data recording
• Generate random frequency steps ➜ compressive sensing
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Conclusion: Future work
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• Real-time kinematic (RTK) positioning system
• Autonomous flying
• Accurate distance measurement
Thank you!